Ignition time controlling device in contactless ignition devices for internal combustion engines

Abstract

An ignition time controlling device having a trigger circuit employing a programmable unijunction transistor which will be ON at a timing when a primary short-circuiting current of an ignition coil is at or a little past a peak. The device includes a charging and discharging circuit for the primary short-circuiting current; a switching controlling circuit interrupting the primary short-circuiting current when the trigger circuit is ON; an ignition coil inducing a high voltage in a secondary coil when the primary short-circuiting current is interrupted; a spark plug generating a spark on receiving the high voltage of the secondary winding and an angle advancing circuit connected between the programmable unijunction transistor and the switching controlling circuit. The angle advancing circuit breaks over at a set value of the primary short-circuiting current or the voltage on the primary winding of the ignition coil and operates the switching controlling circuit prior to the operation of the programmable unijunction transistor.

I claim: 
     
       1. An ignition timing control for a contactless ignition device for internal combustion engines comprising a trigger circuit having a programmable unijunction transistor which will be ON when the primary short-circuiting current of an ignition coil is at or a little past its peak, a charging and discharging circuit for the primary short-circuiting current, a switching controlling circuit interrupting the primary short-circuiting current when said trigger circuit is ON, an ignition coil inducing a high voltage in a secondary winding when the primary short-circuiting current is interrupted by said switching controlling circuit, a spark plug generating a spark on receiving the high voltage of the above mentioned secondary winding and an angle advancing circuit connected between said programmable unijunction transistor and said switching controlling circuit, said angle advance circuit breaking over at a set value of the primary short-circuiting current or the voltage on the primary winding of the ignition coil and operating the switching controlling circuit prior to the operation of said programmable unijunction transistor. 
     
     
       2. The timing control according to claim 1, wherein an ignition coil protecting circuit is connected across the ends of the primary winding of the ignition coil, said ignition coil protecting circuit being made conductive when the voltage between both ends of said primary coil reaches a set level to short-circuit both ends of the primary coil. 
     
     
       3. The timing control according to claim 1 wherein an electronic part protecting circuit comprising a diode and resistance connected in series, is connected in parallel with the switching controlling circuit for interrupting the primary short-circuit current. 
     
     
       4. The timing control according to claim 1 wherein an over rotation preventing circuit comprising a series circuit of a thyristor and capacitor, is connected to the angle advancing circuit so that the capacitor may be charged through the above mentioned thyristor at a positive or negative half cycle of the ignition coil to meanwhile delay the operation of the switching transistor.